This invention relates generally to diagnostic imaging methods and apparatus, and more particularly, to methods and apparatus that provide for tomographic reconstruction view weighting methods and apparatus.
In the past, image quality in cardiac CT (Computed Tomography) imaging has been fundamentally limited by temporal resolution of the system. For nearly all patients and heart rates, temporal resolution proved to be the limiting factor in evaluation of cardiac structures and assessment of coronary artery stenosis. Half-scan reconstruction algorithms sought to maximize temporal resolution at the expense of spatial resolution and contrast to noise characteristics in the images. Based on sampling theory, projection views from at least 180 degrees must be used to properly reconstruct an image without aliasing artifacts.
As the temporal resolution of CT systems has increased, some low heart rate exams are now no longer temporal resolution-limited. This trend will only continue as the temporal resolution of CT systems is increased. For instance, using an ECG-gated half-scan reconstruction technique with a rotation speed of 0.35 sec, a temporal resolution of 227 ms or greater can be achieved. Based on analysis in the literature, the rest period duration of the coronary arteries at low heart rates can be up to 300-400 ms. In these patients, diagnosis may not be limited by temporal resolution in the images, but by spatial resolution and noise limitations. For certain patients, it makes sense to balance the temporal, spatial, and noise characteristics in the image. This can be achieved by applying a patient-adaptive partial-scan reconstruction technique as described below.